SIMFEROPOL, Ukraine -- A high-ranking member of the Crimean Tatar assembly has begun a hunger strike at the facility where he awaits trial for allegedly organizing "mass disorder" ahead of Russia's annexation of Crimea.

Ahtem Ciygoz began his protest on May 6 after being placed in solitary confinement this week at the Simferopol facility, assembly first deputy chairman Nariman Celal told RFE/RL.

It it not known why Ciygoz was sent to solitary confinement.

Ciygoz is a deputy chairman of the assembly, or Mejlis. He was arrested in late January by Russian authorities for his alleged role in clashes with pro-Russian demonstrators in February 2014, a month prior to Moscow's annexation of Crimea.

He was charged with organizing deadly mass disorder in relation to the clashes, which took place outside the regional parliament building in the Crimean capital, Simferopol.

Ciygoz was placed in pretrial detention and that detention was subsequently extended until May 19.

Armed men in unmarked uniforms seized the parliament building on February 27, 2014, the day after the clashes in which two died. Russia annexed the Black Sea peninsula after a March 16 referendum that was dismissed by Kyiv and the West as illegitimate.

Since January, several Crimean Tatar activists have been arrested for their roles in the clashes.

Eskender Bariyev of the Committee to Protect Crimean Tatars' Rights wrote on Facebook that activist Mustafa Degermenci was taken away on May 7 by a group of armed men in the village of Hrushivka.

According to Bariyev, Degermenci's parents were told that their son might be charged with taking part in the clashes outside the Crimean parliament.

In April, Crimea's Russian authorities arrested Eskender Nebiyev, a cameraman for a Crimean Tatar television channel that was shut down on April 1. Nebiyev was also arrested over the clashes outside parliament.

In March, Crimean Tatar activist Talyat Yunusov was arrested and charged with assaulting a man during the clashes.

Activists Iskender Kantemirov and Ali Asanov were earlier arrested in connection with the clashes.

Activists say Crimean Tatars have faced discrimination, pressure, and abuse for their opposition to the annexation.